Bio Exam 2 Review
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Direction an impulse follows
o Dendrite  cell body  axon
Describe a neuron at rest in terms of Na+ and K+ charge on either side of the membrane and
voltage
o Resting potential – axon is not conducting an impulse
 Inside of the neuron more negatively charged than the outside
 Higher concentration of Na+ ions outside the axon and higher conc. of K+
ions inside the axon
 Voltage resting potential of: -65mV (on the inside of the axon)
Describe how the resting membrane potential is maintained by an ion pumping mechanism
o K+ ions have tendency to leak out by diffusion thru channel proteins
o Small amts of sodium ions leak in and must be pumped out
o Membrane contains sodium/potassium ion exchange pumps
o Energy of 1 ATP can move 3 Na+ out and 2 K+ into the cell
 This produces polarization
Describe what action potential is
o Rapid change in polarity across axonal membrane as nerve impulse occurs
o Wave of depolarization from -65mV to +40mV (action potential)
o Threshold – minimum voltage needed to cause an action potential
 All-or-nothing event
o Inside of the neuron becomes positive and outside become negative
 Entrance of sodium ions into neuron, exit of potassium ions
o During short recovery period before another action potential (refractory) – sodium
gates are shut and potassium gates are opened
Describe the characteristics of the refractory period of neuron stimulation
o Na+ gates are unable to open
o Additional impulses cannot be propagated until proper orientation is restored by
sodium/potassium pump
o Action potential is unidirectional (cannot move backwards)
For sodium to accumulate rapidly in a neuron  stimulus above the threshold must open
sodium gates in an accelerating manner
Describe the physical relationship between neurons and muscle fibers
o Nerve impulses travel across the synapse btw cells
o Chemical synapse – junction btw neuron and adjacent cell separated by synaptic cleft
 Synaptic cleft – separates synaptic knob from receiving neuron
 Presynaptic cell – releases neurotransmitter molecules into the cleft
 Postsynaptic cell – neurotransmitter binds to receptors on the
membrane
Explain the function of Schwann cells in the nervous system
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Speed of the action potential depends on diameter of the axon and presence of
Schwann cells
 Schwann cells form insulated myelin sheath
 Nodes of Ranvier increase speed of propagation thru salutatory conduction
(action potential jumps from node to node)
 Impulses jump around insulation formed by Schwann cells
Describe the characteristics of inhibitory and excitatory synapses
o Excitatory synapse – if neurotransmitter drives cell’s membrane to threshold of an
action potential
 Permeability to sodium increased
o Inhibitory synapse – drive cell’s membrane away from threshold
 Permeability to potassium and/or chlorine increased
Identify the components of a reflex arc (text pg. 693 figure 37.13)
o Hand touches a sharp pin  Sensory receptors generate nerve impulses  move along
sensory axon  thru dorsal root ganglion  spinal cord
 In spinal cord neurons pass signals to interneurons in gray matter
o Interneuron  cell body of motor neuron  ventral root  axon of motor neuron 
effector (muscle)
 Effector – response to stimulus
 Muscle contracts so you withdraw your hand from the pain
Explain the process of cephalization
o Cephalization – having a well-recognized anterior head with a brain and sensory
receptors
o Evolutionary result of the layering of more and more nervous tissue over reflex
pathways of ancient origin
Describe the evolution of the brain in relation to its growth in size
o Nerve cord underwent series of expansions leading to form the brain and spinal cord
o Cerebrum shows greatest increase in size from lower vertebrates to humans
Describe the functions of the sympathetic and parasympathetic nervous systems
o Both:
 Function automatically and involuntarily
 Innervate all internal organs
 Utilize 2 neurons and 1 ganglion for each impulse
 Breathing rate and blood pressure are regulated by reflex actions to maintain
homeostasis
o Sympathetic - “fight or flight” response
 Accelerates heartbeat and dilates bronchi  muscles need supply of glucose
and oxygen to defend or flee
 Inhibits digestion
 Neurotransmitter released is norepinephrine
o Parasympathetic – “housekeeper” system
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 Promotes internal responses resulting in a relaxed state
 Causes eye pupil to constrict
 Promotes digestion
 Retards heartbeat
 Neurotransmitter released is acetylcholine
Describe the functions of the major parts of the human brain (cortex, medulla oblongata,
cerebellum, cerebrum, pons, etc)
o Cerebrum – largest part of the brain
 Center of consciousness and intelligence
 Corpus callosum – means by which cerebral hemispheres communicate
 Cerebral cortex – four surface lobes (frontal, parietal, occipital, temporal)
o Hypothalamus
 Maintains homeostasis
 Controls pituitary gland (link btw nervous and endocrine systems)
 Deals w/ basic drives like hunger, sex, thirst
o Thalamus
 Central relay station for impulses traveling from body or brain to cerebrum
 Channels sensory impulses (except for smell)
 Pineal gland – secretes melatonin
o Cerebellum
 Coordinates muscles, maintain equilibrium, posture
 Learning of new motor skills
o Brain stem – contains medulla oblongata, pons, midbrain
 Midbrain – relay station btw cerebrum and spinal cord; reflex centers for visual,
auditory responses
 Pons – (bridge btw cerebellum and CNS) helps regulate breathing rate; reflex
centers for head movements
 Medulla oblongata
 Regulates heartbeat, breathing, vasoconstriction, reflex centers for
vomiting, coughing, sneezing, hiccupping, swallowing
o Hindbrain – cerebellum, pons, medulla
o Brain stem – medulla oblongata, pons, midbrain
o Forebrain – cerebrum, thalamus, hypothalamus
Identify the major parts of the human brain (look at end of study guide)
List the major functions of each lobe of the brain
o Left frontal lobe – Broca’s area  ability to speak
 If damaged – able to form thoughts but can’t express them
o Occipital – vision
o Temporal – auditory
o Parietal – taste
o Somatosensory area – processes and analyzes info from skin and muscles
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Limbic system – blends higher mental functions and primitive emotions
 Hippocampus – aware of past experiences
 Amygdala – causes experiences to have emotional overtones
Relate various EEG tracings to brain activity
o Various activities are associated w/ various degrees of electrical activity and recorded as
EEGs
 Greater degree of consciousness  greater freq. and lower amplitude
o Differences in intensity of a stimulus are indicated by the number of nerves activated
and are encoded in the freq. of action potentials on a single axon
Regulation of organ systems: stimulus, receptor, integrator, effector, response
Know basic types of sensory receptors
o Mechanoreceptors – detect changes in pressure, position, acceleration; receptors for
touch, stretch, hearing, and equilibrium
o Thermoreceptors – detect radiant energy, including infrared
o Nociceptors – pain receptors that detect tissue damage
o Chemoreceptors – detect ions or molecules; include olfactory and gustatory (taste)
receptors
o Osmoceptors – detect changes in conc. of extracellular fluids
o Photoreceptors – detect the energy of visible and UV light
Explain how the brain interprets the type and intensity of a stimulus
o Neurons in the brain can interpret incoming action potentials only in specific ways
 Ex. receptors from eyes only respond to light
o Strong stimulation of a receptor  greater freq. of action potentials and more neurons
fire
Know which structures function for hearing and which for equilibrium
o Hearing – auditory canal, tympanic membrane, oval window, cochlea, vestibular canal,
tympanic canal, cochlear canal, organ of Corti, basilar membrane
o Equilibrium – semicircular canals, ampulla, utricle, saccule, endolymph
Label the major structures of the sensory organs (ear, eye) – look at end of study guide
Identify and describe the function of the various kinds of joints
o Fibrous – immovable; no gap btw bones (sutures btw cranial bones)
o Cartilaginous – slightly moveable; the 2 hip bones are slightly moveable bc they are
joined by cartilage; btw vertebrae
o Synovial – move freely; stabilized by ligaments; ligaments bind bone to bone; synovial
fluid lubricates the joint
 Double-jointed – ligaments are unusually loose
Distinguish bones of appendicular vs. axial skeleton
o Axial – midline of body
 Skull (frontal, zygomatic, maxilla, mandible), vertebral column, thoracic cage
(sternum, ribs, costal cartilages), sacrum, coccyx
o Appendicular –
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Pectoral girdle – clavicle, scapula, humerus, radius, ulna,
carpals/metacarpals/phalanges
 Pelvic girdle and lower limb – coxal, femur, patella, tibia, fibula,
tarsals/metatarsals/phalanges
Know what happens during muscle contraction
o Muscle stimulated to contract by motor nerve fibers
o  impulse travels down motor neuron and arrives at axon terminal
o  ACh (neurotransmitter) released into synaptic cleft
o  ACh diffuses across cleft and binds to receptors in sarcolemma
o  sarcolemma generates impulses  spread down T tubules into sarcoplasmic
reticulum  calcium released  causes filaments in sarcomere to slide past one
another
o  sarcomere contraction  myofibril contraction  muscle fiber  muscle
contraction
List the proteins involved in the various phases of muscle contraction (4)
o Actin – slide past myosin filaments (mechanism of muscle contraction)
o Myosin – breaks down ATP for energy  attach to thin filaments (actin), exert tension,
perform power stroke that causes thin filaments to slide past, shortening the muscle
o Tropomyosin – wind around actin filament; block binding sites on actin filaments under
resting conditions
o Troponin – when combined with calcium  change shape and displace trypomyosin 
binding sites exposed
Distinguish btw dark and light bands, what the zones are
o Striated appearance of skeletal muscle due to light and dark regions caused by
overlapping of filaments
o Striations formed by placement of sacromeres
o Sarcomere extends btw 2 dark lines (Z lines)
 2 types of protein filaments
 Thick filaments made up of myosin
 Thin filaments made up of actin
o I band is light colored bc only contains actin filaments attached to a Z line
o A band – dark regions contain overlapping actin and myosin
o H band – only myosin filaments
T tubule system in the muscle fiber is to convey impulses quickly thruout the cell
Part II
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Definition of reciprocal innervation, related to contraction and inhibition of antagonistic muscles
o Antagonistic pairs – contraction of one muscle produces forces opposite to those
generated by contraction of the other
o Contraction of opposing muscles must be inhibited while muscles w/ desired action are
excited
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o So contraction of muscle results in simultaneous relaxation of its antagonist
Explain the activity of fat soluble vs. water soluble hormones
o Steroid hormones are lipid soluble (fat soluble) which is why they don’t need a
membrane receptor
o Water soluble – cannot cross plasma membrane of target cells so must bind to receptor
o Fat soluble – lipid-soluble and can readily cross plasma membrane
Know how 3 basic types of signaling molecules are distributed or transported (hormones,
neurohormones, and neurotransmitters)
o Hormones – secreted from endocrine glands, carried by bloodstream to target cells
thruout body
o Neurohormones – released by neurosecretory cells into bloodstream to target cells
o Neurotransmitters – secreted from neurons and act on immediately adjacent target
cells for short time (responsible for transmission across a synapse; stored at end of
axons)
Know what produces signaling molecules
Diagram of relationship btw hypothalamus and pituitary (posterior and interior)
o Pituitary – small compound gland located at the back of the skull just above the roof of
the mouth
o Posterior – does not produce hormones but does store and release 2 neurosecretory
hormones produced by hypothalamus
o Anterior – glandular and produces at least 6 hormones and controls the secretion of the
other endocrine glands
Know what hormones and neurohormones are produced and secreted by hypothalamus and
pituitary gland
o Pituitary posterior lobe secretions
 Oxytocin (mammalian reproduction) and ADH (controls body’s water and solute
levels)
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Both hormones produced by neurons w/ origin in hypothalamus and terminals
in posterior lobe of pituitary
o Pituitary anterior lobe secretions
 Hypothalamus influences secretions of these hormones
 ACTH, TSH – affect other glands
 FSH, LH, growth hormone/STH, prolactin – do not affect other glands
Know function of parathyroid hormone, FSH, oxytocin
o Parathyroid hormone – respond to changing levels of calcium in the blood
 Drop in calcium levels  PTH levels rise  calcium removed from bone and
vitamin D activated
 Calcium levels rise  PTH levels reduced
o FSH – (follicle-stimulating hormone) stimulates egg formation in females and sperm
formation in males
o Oxytocin – causes uterine contractions in childbirth and milk letdown when baby is
nursing (positive feedback)
Know basic advantages and disadvantages of asexual and sexual reproduction
o Difficulties must be overcome for opposite sex reproduction
 Timing  male and female gametes must be available at the same time
 Hard to find potential mate of same species
 External fertilization in water requires large numbers of gametes
 Internal fertilization req. penis to enter vagina and transfer sperm
 Energy is set aside for nourishing offspring
o Advantages
Distinguish btw direct and indirect development, 2 types of metamorphosis
o Metamorphosis – change in form that some animals undergo during development
 Incomplete metamorphosis – lacks a pupal stage and nymphs look like adults
Know structures of male reproductive system
o 2 gonads (testes) within the scrotum
 Each testis has 2 functional parts
 Seminiferous tubules – where sperm are produced; tightly coiled tubes
 Interstitial cells – produce and secrete sex hormones (testosterone)
 Penis – cylindrical copulatory organ used to transfer sperm into vagina
 3 columns of spongy erectile tissue
 During arousal  nervous reflexes cause increase in blood flow to penis
 blood fills and distends the erectile tissue  penis stiffens and
increases in size
o Cause an erection
o Failure to achieve in erection – impotency
o Testes – produce sperm and sex hormones
o Epididymides – sites of maturation and some storage of sperm
o Vasa deferentia – conduct and store sperm
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o Seminal vesicles – contribute fluid to semen
o Prostate gland – contributes fluid to semen
o Urethra – conducts sperm and urine
o Bulbourethral glands – contribute fluid to semen
o Penis – organ of copulation (sexual union)
Trace movement of sperm cells
o Sperm move from testis  epididymis (for maturation and storage)  vas deferens 
ejaculatory ducts  urethra (outside of penis)
o Sperm formation
 Diploid spermatogonia undergo mitosis  primary spermatocytes undergo
meiosis I  haploid secondary spermatocytes undergo meiosis II  haploid
spermatids  mature sperm
Testosterone, how/where produced and functions
o Produced by Leydig cells btw lobes in the testes
o Maturation of sperm, normal development and functioning of male reproductive
organs, brings abt and maintains secondary sex characteristics that develop at puberty,
greater muscular development
Compare and contrast male and female reproductive systems in terms of function
o Estrogen and progesterone have same effect in females and males
Fertilization  cleavage  blastula  gastrula
Fertilization in human reproductive system, where it occurs, what follows
o Triggered by sperm penetration; one sperm enters the egg and their nuclei fuse; diploid
zygote forms
o Endometrium receives the embryo which becomes embedded in the lining
Zones of gastrulation, basic tissue layers that are formed and what organs they lead to
o Gastrulation – gene activity in individual cells dominates future development
o Basic tissue layers:
 Endoderm – inner layer; gives rise to lung epithelium, inner lining of gut,
accessory glands
 Mesoderm – intermediate layer; gives rise to muscle, organs of circulation,
reproduction and excretion, most of internal skeleton, connective tissue layers
of the gut and body covering
 Ectoderm – surface layer; gives rise to nervous system and outer layer of body
covering
Know development of embryo
o Cleavage – resulting in multicellular embryo; cell division occurs without cell growth
(embryo occupies same space as original zygote); increases number of cells, does not
change original volume of egg’s cytoplasm
o First forms solid ball of cells (morula)
 Blastula forms next (hollow sphere of cells)
 Cavity within blastula is blastocoel
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Embryo becomes a blastocyst when fluid entering the cavity lifts the inner cell
mass away from surface layer on all but one side
o Embryo formation takes 2 weeks; embryonic period lasts from 3rd to 8th week
Pattern formation (cytoplasmic globalization, embryonic induction)
o Embryonic induction – ability of one embryonic tissue to influence the development of
another tissue
1st Practice Exam results – 24/50
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Difference in “sensation” and “perception” when referring to a stimulus lies in understanding
the significance of a stimulus
Identifying parts of the brain (medulla, pons, corpus callosum)
Ciliary muscle controls the shape of the lens to allow focusing
Purpose of T tubule system in the muscle fiber is to convey impulses quickly thruout the cell
Synovial cell diagram & tendon
FALSE – in a resting muscle energy is stored in the form of tropomyosin
During contraction  cross-bridges of muscle filaments are broken and reformed
FALSE – although hormones are carried to all parts of the body, they produce effects only in cells
with proper receptors
Diagram of anterior and posterior
Control over milk production, water balance, and labor in childbirth is mediated by posterior
pituitary
Where sperm cells stored
Where mitochondria are in sperm (movement)
HCG – not responsible for sperm production
FALSE – female will normally produce more gametes than her male counterpart
Where fertilization occurs
Area illustrated on fertilized egg – layer  formed opposite from where sperm enters egg
During pregnancy, implantation occurs at blastocyst
Amnion – fluid-filled sac immediately surrounding embryo
Urea – diffuses in greater amounts from fetal blood to mother’s blood
46/50
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FALSE – stimulus will generate impulses that are different depending on where the signals are
sent in the brain
Differences in intensity of a stimulus are indicated by number of nerves activated
Although hormones are carried to all parts of the body, they produce effects only in cells with
proper receptors